Vegetarians cobalamins

Very small amounts of cobalamin are required each day (<5 i.g) and the diet normally provides plenty more than the minimum, so dietary B12 deficiency is uncommon, except in very strict vegetarians. Pernicious anaemia arises when a defect in the stomach results in too little secretion of a protein called intrinsic factor, without which, cobalamin cannot be absorbed in the ileum of the small intestine. 

The most likely reason for cobalamin deficiency is pernicious anemia (failure to absorb vitamin B 2 in the absence of intrinsic factor from parietal cells). Vitamin Bjj absorption also decreases with aging and in individuals with chronic pancreatitis. Less common reasons for Bjj deficiency include a long-term completely vegetarian diet (plants don t contain vitamin Bjj) and infection with Diphyllobothrium latum, a parasite found in raw fish. Excess vitamin B,2 is stored in the body, so deficiencies develop slowly. 

Vitamin B12 (cobalamine) is one of the most complex low-molecular-weight substances occurring in nature. The core of the molecule consists of a tetrapyrrol system (corrin), with cobalt as the central atom (see p. 108). The vitamin is exclusively synthesized by microorganisms. It is abundant in liver, meat, eggs, and milk, but not in plant products. As the intestinal flora synthesize vitamin B12, strict vegetarians usually also have an adequate supply of the vitamin. 

Strict vegetarian diet or after diseases affecting cobalamin absorption. The main effects of vitamin deficiency are pernicious anemia, macrocytosis, and neurological problems. A particularity of this vitamin is that it can be stored especially in the liver and kidneys. 

Cyanocobalamin and the derivative hydroxo-cobalamin, given IM or deep subcutaneously, are indicated for treating vitamin B12 deficiency. Only in strict vegetarians oral preparations may be effective. Oral preparations with added intrinsic factor mostly are not reliably in patients with pernicious anemia. More than half the dose of cyanocobalamin injected is excreted in the urine within 48 hours and the therapeutic advantages of doses higher than 100 pg are questionable because of this rapid eiimination. As... 

Vitamin B12, cobalamin or cyanocobaltamin, C63H88CoN14Oi4P, has the most complicated structure of the B vitamins. It contains one atom of cobalt in its molecule. It is required in minute amounts but without it the manufacture of proteins and red blood cells is affected. A diet which is deficient in liver, eggs, meat, fish or milk can lead to pernicious anaemia. Vegetarians are often advised to take vitamin B12 supplements. 

Vitamin B12 (cyancobali-min, cobalamin) Protein and fatty acid metabolism production of red blood cells maintenance of nervous system, concentration and memory. Clams, oysters, beef, eggs and dairy products. Not found in many plant products strict vegetarians may need to consider Bi2 supplements. 2 mg No... 

Vitamin B12 is stable to temperatures up to 250°C (482°F) in acidic or neutral solutions. Dietary B12 deficiency is rare among meat eaters but not in strict vegetarians. The average total body content of vitamin B12 is about 2.5 mg, most of which is in the liver (1 /u,g of Bi2 per gram of hepatic tissue). There is extensive reutilization of cobalamin and an active enterohepatic circulation. The principal disease caused by vitamin B12 deficiency is megaloblastic anemia. Deficiency also causes neurological abnormalities that become irreversible if allowed to persist. 

Underlying problem Lack of cobalamin intake with complete vegetarian diet (vegan). 

Cobalamin (vitamin Bj ) deficiency Inadequate uptake of cobalamin from the diet often due to lack of intrinsic factor an intestinal transport protein or less often due to unaugmented vegetarian diet that strictly avoids meat or meat products, the source of dietary cobalamin. 

Bj2 (cobalamin) Meat, fish, eggs, milk Coenzyme in amino acid metabolism Rare except in vegetarians pernicious anemia... 

V.B12 occurs predominantly in animal tissues and animal products. It is synthesized principally by bacteria. Green plants contain little or no V.B,2. Deficiency symptoms are sometimes observed in strict vegetarians, most often in breast-fed infants whose mothers consume no animal products. The body reserves of cobalamin are usually so large that an adult can survive for many years on them in the absence of a dietary intake. 

Cobalamin deficiency a realistic concern for vegans and vegetarians. 

Herbert, V., 1994. Staging vitamin B-12 (cobalamin) status in vegetarians. The American Journal of Clinical Nutrition. 59(suppl) 1213S-1222S. 

Vitamin Bj2 is used for the enrichment of some foods (such as breakfast cereals, soy products, energy bars and yeast extract spread) and which maybe the source of corrinoids for strict vegetarians and vegans. Along with other vitamins, vitamin Bjj is added to many multivitamin preparations and to food supplements. Cyanocobal-amin, which is used in most supplements, is readily converted into the coenzyme forms of cobalamin (methylcobalamin and 5 -deoxyadenosylcobalamin) in the human body. 

Animals, plants, and fungi are incapable of producing cobalamin it is the only vitamin that is exclusively produced hy microorganisms, particularly by anaerobes (Roth et al. 1996 Martens et al. 2002 Smith et al. 2007). Furthermore, biochemical and genomic data indicate that only a few bacteria and archaea possess the abOity to produce this vitamin (Roth et al. 1996 Rodionov et al. 2003). Adult ruminant animals and strict vegetarians can obtain the vitamin in specialized bacteria present in the rumen. Humans do not have such microbiota in their small intestine and must absorb the co-enzyme from natural sources such as animal meats (especially liver and kidney), fish, eggs, and pharmaceutical products (Herbert 1996). 

---